1. Field of the Invention
The invention pertains to image analysis, more specifically to a method and a system for image scaling output timing calculation.
2. Description of Related Art
Digital image data generally defines one or more frames. A frame is an image displayed for viewing on a display screen or panel at one time. Each frame includes a rectangular array of pixels. Each pixel has one or more values, for example a gray scale value for a monochrome display or RGB values for a color display. In order to run the many individual multimedia products on the market, computer systems are required to display many different programs that generate different types of images at different times. Conventional computer systems may use a graphics system to generate graphics and video pixel data for display on a display device. The pixel data is passed to the display device and produces the images viewed on the display device. With the emergence of new display technologies, the transition from one display resolution on a particular display format to another presents a host of problems when the same application is run on two different computer systems with varying display resolutions. Common display resolution include those shown in Table 1 indicating the number of pixels in each dimension.
TABLE 1VGA640480SVGA800600XGA1024768SXGA12801024UXGA16001200HDTV1280720
Where the resolution or sample rate of the display device matches the resolution of a particular image data being displayed, the image data can be displayed directly; or if not, the image data may have to be scaled or formatted to the appropriate format acceptable to the particular display device. Scaling can be done in either vertical or horizontal or both dimensions and the sample rates can be scaled up or down. Scaling becomes particularly important in the case of pixelated display systems in display devices such as liquid crystal displays (LCDs), projectors, flat panel displays, PDP, FED, EL, DMD, etc., that have a pixel structure.
Image scaling is typically accomplished using sample rate conversion where the sample rate converters scales by a rational number UM where L and M are positive integers. U.S. Pat. Nos. 4,020,332, 4,682,301, and 6,339,434 all disclose image scaling using integer conversion rates.
However, in each of these disclosures, performing image scaling from one display format to another and keeping the same frame rate to render the last line of each output frame from being either a short line or a long line that some display panels cannot tolerate. Accordingly, a need remains for improvements in image scaling schemes to eliminate short lines or long lines. Particularly, a need exists for a system that improves the performance of image scaling between display devices at lower costs and higher performance.